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Red Thunder, here we come!

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  Red Thunder, here we come! Joe Bernstein <joe@sfbooks.com> - 2015-09-11 21:01 -0700
    Re: Red Thunder, here we come! Don Kuenz <garbage@crcomp.net> - 2015-09-12 17:01 +0000
      Re: Red Thunder, here we come! Cryptoengineer <treifamily@gmail.com> - 2015-09-12 15:24 -0500
        Re: Red Thunder, here we come! Don Kuenz <garbage@crcomp.net> - 2015-09-12 22:31 +0000
          Re: Red Thunder, here we come! Cryptoengineer <treifamily@gmail.com> - 2015-09-12 21:43 -0500
        YASID:  Moon in a very low orbit. Greg Goss <gossg@gossg.org> - 2015-09-13 01:33 -0600
          Re: YASID:  Moon in a very low orbit. wdstarr@panix.com (William December Starr) - 2015-09-13 03:51 -0400
            Re: YASID:  Moon in a very low orbit. tmcd@panix.com (Tim McDaniel) - 2015-09-20 23:23 +0000
              Re: YASID:  Moon in a very low orbit. Cryptoengineer <treifamily@gmail.com> - 2015-09-20 19:56 -0500
                Re: YASID:  Moon in a very low orbit. Robert Carnegie <rja.carnegie@excite.com> - 2015-09-20 20:18 -0700
                Re: YASID:  Moon in a very low orbit. tmcd@panix.com (Tim McDaniel) - 2015-09-22 05:46 +0000
                  Re: YASID:  Moon in a very low orbit. "J. Clarke" <j.clarke.873638@gmail.com> - 2015-09-22 04:04 -0400
          Re: YASID:  Moon in a very low orbit. Cryptoengineer <treifamily@gmail.com> - 2015-09-13 10:31 -0500
            Re: YASID:  Moon in a very low orbit. "Michael R N Dolbear" <me@privacy.net> - 2015-09-13 19:41 +0100
              Re: YASID:  Moon in a very low orbit. Cryptoengineer <treifamily@gmail.com> - 2015-09-13 21:15 -0500
                Re: YASID:  Moon in a very low orbit. "J. Clarke" <j.clarke.873638@gmail.com> - 2015-09-14 06:05 -0400
                  Re: YASID: Moon in a very low orbit. Dimensional Traveler <dtravel@sonic.net> - 2015-09-14 18:47 -0700
            Re: YASID:  Moon in a very low orbit. Robert Carnegie <rja.carnegie@excite.com> - 2015-09-13 21:49 -0700
              Re: YASID:  Moon in a very low orbit. Greg Goss <gossg@gossg.org> - 2015-09-14 10:21 -0600
                Re: YASID: Moon in a very low orbit. nebusj-@-rpi-.edu (Joseph Nebus) - 2015-09-14 20:26 +0000
    Re: Red Thunder, here we come! Robert Bannister <robban@clubtelco.com> - 2015-09-14 11:43 +0800
      Re: Red Thunder, here we come! "J. Clarke" <j.clarke.873638@gmail.com> - 2015-09-14 06:16 -0400
        Re: Red Thunder, here we come! "Brian M. Scott" <b.scott@csuohio.edu> - 2015-09-14 06:24 -0400

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#422601 — Red Thunder, here we come!

So apparently while I wasn't looking a bunch of people have been 
launching stuff into the stratosphere, including, several years ago, two 
seventeen-year-old boys:

<http://www.space.com/14397-teens-lego-man-space-stratosphere.html>

Well, last weekend, not all that far from me in Seattle, came something 
to rather more than trump that:

<http://www.geekwire.com/2015/two-seattle-girls-launched-a-balloon-to-the-edge-of-space-this-weekend-and-have-the-video-to-prove-it/>

By "girls", in this case, it turns out, is meant one ten-year-old and 
one eight-year-old.  They apparently got their balloon to go 78,000 
feet up, which is 2,000 less than the teenagers in 2012.

ObSF in subject.

Joe Bernstein

-- 
Joe Bernstein, writer and tax preparer                 <joe@sfbooks.com>

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#422643

Joe Bernstein <joe@sfbooks.com> wrote:
> So apparently while I wasn't looking a bunch of people have been
> launching stuff into the stratosphere, including, several years ago, two
> seventeen-year-old boys:
>
> <http://www.space.com/14397-teens-lego-man-space-stratosphere.html>
>
> Well, last weekend, not all that far from me in Seattle, came something
> to rather more than trump that:
>
> <http://www.geekwire.com/2015/two-seattle-girls-launched-a-balloon-to-the-edge-of-space-this-weekend-and-have-the-video-to-prove-it/>
>
> By "girls", in this case, it turns out, is meant one ten-year-old and
> one eight-year-old.  They apparently got their balloon to go 78,000
> feet up, which is 2,000 less than the teenagers in 2012.
>
> ObSF in subject.

The Qu8k rocket made it to 121,000' at Black Rock BALLS 20 in 2011.
https://www.youtube.com/watch?v=rvDqoxMUroA . IIRC one of the BALLS
founders expects orbital flight real soon now.

--
 ,-.                              There was a young lady named Bright
 \_/                              Whose speed was far faster than light;
{|||)<   Don Kuenz KB7RPU            She set out one day
 / \                                 In a relative way
 `-'                              And returned on the previous night.

What you do speaks so loud that I can not hear what you say. - Emerson.

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#422655

Don Kuenz <garbage@crcomp.net> wrote in news:20150912a@crcomp.net:

> 
> Joe Bernstein <joe@sfbooks.com> wrote:
>> So apparently while I wasn't looking a bunch of people have been
>> launching stuff into the stratosphere, including, several years ago,
>> two seventeen-year-old boys:
>>
>> <http://www.space.com/14397-teens-lego-man-space-stratosphere.html>
>>
>> Well, last weekend, not all that far from me in Seattle, came
>> something to rather more than trump that:
>>
>> <http://www.geekwire.com/2015/two-seattle-girls-launched-a-balloon-to-
>> the-edge-of-space-this-weekend-and-have-the-video-to-prove-it/> 
>>
>> By "girls", in this case, it turns out, is meant one ten-year-old and
>> one eight-year-old.  They apparently got their balloon to go 78,000
>> feet up, which is 2,000 less than the teenagers in 2012.
>> ObSF in subject.

There's a bit of a fad for launching weather balloons to high altitudes,
and including a small figurine or object in view of a camera, most for
the sheer incongruity of seeing Hello Kitty against curving horizon.

> The Qu8k rocket made it to 121,000' at Black Rock BALLS 20 in 2011.
> https://www.youtube.com/watch?v=rvDqoxMUroA . IIRC one of the BALLS
> founders expects orbital flight real soon now.

'Orbital flight'? Or 'reaching orbital height'? There's a huge
difference in energy and guidance requirements. The latter is
much easier to do.

pt

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#422662

Cryptoengineer <treifamily@gmail.com> wrote:
> Don Kuenz <garbage@crcomp.net> wrote in news:20150912a@crcomp.net:
>
>>
>> Joe Bernstein <joe@sfbooks.com> wrote:
>>> So apparently while I wasn't looking a bunch of people have been
>>> launching stuff into the stratosphere, including, several years ago,
>>> two seventeen-year-old boys:
>>>
>>> <http://www.space.com/14397-teens-lego-man-space-stratosphere.html>
>>>
>>> Well, last weekend, not all that far from me in Seattle, came
>>> something to rather more than trump that:
>>>
>>> <http://www.geekwire.com/2015/two-seattle-girls-launched-a-balloon-to-
>>> the-edge-of-space-this-weekend-and-have-the-video-to-prove-it/>
>>>
>>> By "girls", in this case, it turns out, is meant one ten-year-old and
>>> one eight-year-old.  They apparently got their balloon to go 78,000
>>> feet up, which is 2,000 less than the teenagers in 2012.
>>> ObSF in subject.
>
> There's a bit of a fad for launching weather balloons to high altitudes,
> and including a small figurine or object in view of a camera, most for
> the sheer incongruity of seeing Hello Kitty against curving horizon.
>
>> The Qu8k rocket made it to 121,000' at Black Rock BALLS 20 in 2011.
>> https://www.youtube.com/watch?v=rvDqoxMUroA . IIRC one of the BALLS
>> founders expects orbital flight real soon now.
>
> 'Orbital flight'? Or 'reaching orbital height'? There's a huge
> difference in energy and guidance requirements. The latter is
> much easier to do.

My knowledge of rockets is very limited. So my phrasing is a "punt."
IIRC he uses "orbital" as either a word or a part of a word. But
"suborbital" in the future tense seems wrong because the Qu8k rocket
shows that ?suborbital flight? is a fait accompli?

--
 ,-.                              There was a young lady named Bright
 \_/                              Whose speed was far faster than light;
{|||)<   Don Kuenz KB7RPU            She set out one day
 / \                                 In a relative way
 `-'                              And returned on the previous night.

What you do speaks so loud that I can not hear what you say. - Emerson.

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#422668

Don Kuenz <garbage@crcomp.net> wrote in news:20150912b@crcomp.net:

> 
> 
> Cryptoengineer <treifamily@gmail.com> wrote:
>> Don Kuenz <garbage@crcomp.net> wrote in news:20150912a@crcomp.net:
>>
>>>
>>> Joe Bernstein <joe@sfbooks.com> wrote:
>>>> So apparently while I wasn't looking a bunch of people have been
>>>> launching stuff into the stratosphere, including, several years ago,
>>>> two seventeen-year-old boys:
>>>>
>>>> <http://www.space.com/14397-teens-lego-man-space-stratosphere.html>
>>>>
>>>> Well, last weekend, not all that far from me in Seattle, came
>>>> something to rather more than trump that:
>>>>
>>>> <http://www.geekwire.com/2015/two-seattle-girls-launched-a-balloon-
to-
>>>> the-edge-of-space-this-weekend-and-have-the-video-to-prove-it/>
>>>>
>>>> By "girls", in this case, it turns out, is meant one ten-year-old 
and
>>>> one eight-year-old.  They apparently got their balloon to go 78,000
>>>> feet up, which is 2,000 less than the teenagers in 2012.
>>>> ObSF in subject.
>>
>> There's a bit of a fad for launching weather balloons to high 
altitudes,
>> and including a small figurine or object in view of a camera, most for
>> the sheer incongruity of seeing Hello Kitty against curving horizon.
>>
>>> The Qu8k rocket made it to 121,000' at Black Rock BALLS 20 in 2011.
>>> https://www.youtube.com/watch?v=rvDqoxMUroA . IIRC one of the BALLS
>>> founders expects orbital flight real soon now.
>>
>> 'Orbital flight'? Or 'reaching orbital height'? There's a huge
>> difference in energy and guidance requirements. The latter is
>> much easier to do.
> 
> My knowledge of rockets is very limited. So my phrasing is a "punt."
> IIRC he uses "orbital" as either a word or a part of a word. But
> "suborbital" in the future tense seems wrong because the Qu8k rocket
> shows that ?suborbital flight? is a fait accompli?

Technically, a tossed baseball is in a 'suborbital flight'. Getting up
to 'space' (100km) is probably what he's talking about - the lowest
orbits are higher (160 km). 

Putting something in orbit is an order of magnitude harder, since
you have to get moving at orbital velocity (18k mph). Less than a
dozen countries, and two corporations have put stuff into orbit.

There's a good explanation of the issue here:
http://what-if.xkcd.com/58/

pt

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#422677 — YASID: Moon in a very low orbit.

Cryptoengineer <treifamily@gmail.com> wrote:

>Don Kuenz <garbage@crcomp.net> wrote in news:20150912a@crcomp.net:
>'Orbital flight'? Or 'reaching orbital height'? There's a huge
>difference in energy and guidance requirements. The latter is
>much easier to do.

But what is "orbital height"?  I remember reading an SF short story
about a guy wondering at the various holes and valleys on a planet he
was exploring (Mars?) and realizing just in time that a super-dense
moon was orbiting rather low.

I think of it as a Niven, but probably because I'm confusing it with
There Is A Tide, where the moon was at normal height -- whfg n ovg
qrafre guna hfhny.

(Bs pbhefr, jr abj ernyvmr gung lbh pna'g trg fhpu n qrafr bowrpg
jvgubhg flagurgvp zrnaf, juvpu vf jul gur "Syrrg bs Jbeyqf" ergpba bs
Xabja Fcnpr znqr gur "Gurer vf n Zbba" n qryvorengr genc.

Spoilers for There is a Tide and a much more recent Niven
collaboration above)
-- 
We are geeks.  Resistance is voltage over current.

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#422678 — Re: YASID: Moon in a very low orbit.

In article <d5kn6uFijpuU1@mid.individual.net>,
Greg Goss <gossg@gossg.org> said:

> But what is "orbital height"?  I remember reading an SF short
> story about a guy wondering at the various holes and valleys on a
> planet he was exploring (Mars?) and realizing just in time that a
> super-dense moon was orbiting rather low.
>
> I think of it as a Niven, but probably because I'm confusing it
> with There Is A Tide, where the moon was at normal height [...]

http://www.isfdb.org/cgi-bin/title.cgi?45756

Title: The Holes Around Mars
Author: Jerome Bixby
Year: 1954
Type: SHORTFICTION
Storylen: shortstory
Language: English

Available for free at:

https://www.gutenberg.org/ebooks/32360

-- wds

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#423268 — Re: YASID: Moon in a very low orbit.

In article <mt39us$cmg$1@panix3.panix.com>,
William December Starr <wdstarr@panix.com> wrote:
>In article <d5kn6uFijpuU1@mid.individual.net>,
>Greg Goss <gossg@gossg.org> said:
>
>> But what is "orbital height"?  I remember reading an SF short
>> story about a guy wondering at the various holes and valleys on a
>> planet he was exploring (Mars?) and realizing just in time that a
>> super-dense moon was orbiting rather low.
>>
>> I think of it as a Niven, but probably because I'm confusing it
>> with There Is A Tide, where the moon was at normal height [...]
>
>http://www.isfdb.org/cgi-bin/title.cgi?45756
>
>Title: The Holes Around Mars
>Author: Jerome Bixby
>Year: 1954
>Type: SHORTFICTION
>Storylen: shortstory
>Language: English
>
>Available for free at:
>
>https://www.gutenberg.org/ebooks/32360

"I think it's a calendar! ... Six hundred and eighty-seven squares in
all.  That's how many days there are in the Martian year!"

WTF!  Why would a calendar devised by MARTIANS for Mars be based on
EARTH days?

To be honest, that's straining at a gnat and swallowing a camel -- the
basic mechanism would last for milliseconds to seconds, and even if
it did last, the hyperprecise ercrngrq cngu would be impossible.

-- 
Tim McDaniel, tmcd@panix.com

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#423278 — Re: YASID: Moon in a very low orbit.

tmcd@panix.com (Tim McDaniel) wrote in news:mtnf5c$li7$1
@reader1.panix.com:

> In article <mt39us$cmg$1@panix3.panix.com>,
> William December Starr <wdstarr@panix.com> wrote:
>>In article <d5kn6uFijpuU1@mid.individual.net>,
>>Greg Goss <gossg@gossg.org> said:
>>
>>> But what is "orbital height"?  I remember reading an SF short
>>> story about a guy wondering at the various holes and valleys on a
>>> planet he was exploring (Mars?) and realizing just in time that a
>>> super-dense moon was orbiting rather low.
>>>
>>> I think of it as a Niven, but probably because I'm confusing it
>>> with There Is A Tide, where the moon was at normal height [...]
>>
>>http://www.isfdb.org/cgi-bin/title.cgi?45756
>>
>>Title: The Holes Around Mars
>>Author: Jerome Bixby
>>Year: 1954
>>Type: SHORTFICTION
>>Storylen: shortstory
>>Language: English
>>
>>Available for free at:
>>
>>https://www.gutenberg.org/ebooks/32360
> 
> "I think it's a calendar! ... Six hundred and eighty-seven squares in
> all.  That's how many days there are in the Martian year!"
> 
> WTF!  Why would a calendar devised by MARTIANS for Mars be based on
> EARTH days?

How well was the rotation period of Mars established in 1954? IIRC, at
that time, even canals hadn't been ruled out. 
http://planetary.org/explore/space-topics/mars/mars-calendar.html
tells me that the Martian year is 668 sols or 684 Earth days.
But yeah, it seems a pretty careless error on the author's part.

pt

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#423285 — Re: YASID: Moon in a very low orbit.

On Monday, 21 September 2015 01:56:48 UTC+1, Cryptoengineer  wrote:
> tmcd@panix.com (Tim McDaniel) wrote in news:mtnf5c$li7$1
> @reader1.panix.com:
> 
> > In article <mt39us$cmg$1@panix3.panix.com>,
> > William December Starr <wdstarr@panix.com> wrote:
> >>In article <d5kn6uFijpuU1@mid.individual.net>,
> >>Greg Goss <gossg@gossg.org> said:
> >>
> >>> But what is "orbital height"?  I remember reading an SF short
> >>> story about a guy wondering at the various holes and valleys on a
> >>> planet he was exploring (Mars?) and realizing just in time that a
> >>> super-dense moon was orbiting rather low.
> >>>
> >>> I think of it as a Niven, but probably because I'm confusing it
> >>> with There Is A Tide, where the moon was at normal height [...]
> >>
> >>http://www.isfdb.org/cgi-bin/title.cgi?45756
> >>
> >>Title: The Holes Around Mars
> >>Author: Jerome Bixby
> >>Year: 1954
> >>Type: SHORTFICTION
> >>Storylen: shortstory
> >>Language: English
> >>
> >>Available for free at:
> >>
> >>https://www.gutenberg.org/ebooks/32360
> > 
> > "I think it's a calendar! ... Six hundred and eighty-seven squares in
> > all.  That's how many days there are in the Martian year!"
> > 
> > WTF!  Why would a calendar devised by MARTIANS for Mars be based on
> > EARTH days?
> 
> How well was the rotation period of Mars established in 1954? IIRC, at
> that time, even canals hadn't been ruled out. 
> http://planetary.org/explore/space-topics/mars/mars-calendar.html
> tells me that the Martian year is 668 sols or 684 Earth days.
> But yeah, it seems a pretty careless error on the author's part.

I assume 684 was 687 before finger met keyboard.
But <https://en.wikipedia.org/wiki/Timekeeping_on_Mars>
says it's uneven, so, have a party.

And that a 687 days Mars year is one thing that maybe 
/is/ an Edgar Rice Burroughs first on Mars.

...another author wrote on the topic of Earth visitors
beoming naturalized Martian citizens.  With calendar?

Ancient Egypt had a 360 days ceremonial calendar 
and lasted to watch it slide right around the actual year.

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#423361 — Re: YASID: Moon in a very low orbit.

In article <XnsA51BD513C1A3Bmelchizedek@216.166.97.131>,
Cryptoengineer  <treifamily@gmail.com> wrote:
>tmcd@panix.com (Tim McDaniel) wrote in news:mtnf5c$li7$1
>@reader1.panix.com:
>
>> In article <mt39us$cmg$1@panix3.panix.com>,
>> William December Starr <wdstarr@panix.com> wrote:
>>>In article <d5kn6uFijpuU1@mid.individual.net>,
>>>Greg Goss <gossg@gossg.org> said:
>>>
>>>> But what is "orbital height"?  I remember reading an SF short
>>>> story about a guy wondering at the various holes and valleys on a
>>>> planet he was exploring (Mars?) and realizing just in time that a
>>>> super-dense moon was orbiting rather low.
>>>>
>>>> I think of it as a Niven, but probably because I'm confusing it
>>>> with There Is A Tide, where the moon was at normal height [...]
>>>
>>>http://www.isfdb.org/cgi-bin/title.cgi?45756
>>>
>>>Title: The Holes Around Mars
>>>Author: Jerome Bixby
>>>Year: 1954
>>>Type: SHORTFICTION
>>>Storylen: shortstory
>>>Language: English
>>>
>>>Available for free at:
>>>
>>>https://www.gutenberg.org/ebooks/32360
>> 
>> "I think it's a calendar! ... Six hundred and eighty-seven squares in
>> all.  That's how many days there are in the Martian year!"
>> 
>> WTF!  Why would a calendar devised by MARTIANS for Mars be based on
>> EARTH days?
>
>How well was the rotation period of Mars established in 1954?

Nobody should have assumed that it was exactly identical to Earth's,
even for purposes of a farce.

-- 
Tim McDaniel, tmcd@panix.com

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#423365 — Re: YASID: Moon in a very low orbit.

In article <mtqq0h$1tc$1@reader1.panix.com>, tmcd@panix.com says...
> 
> In article <XnsA51BD513C1A3Bmelchizedek@216.166.97.131>,
> Cryptoengineer  <treifamily@gmail.com> wrote:
> >tmcd@panix.com (Tim McDaniel) wrote in news:mtnf5c$li7$1
> >@reader1.panix.com:
> >
> >> In article <mt39us$cmg$1@panix3.panix.com>,
> >> William December Starr <wdstarr@panix.com> wrote:
> >>>In article <d5kn6uFijpuU1@mid.individual.net>,
> >>>Greg Goss <gossg@gossg.org> said:
> >>>
> >>>> But what is "orbital height"?  I remember reading an SF short
> >>>> story about a guy wondering at the various holes and valleys on a
> >>>> planet he was exploring (Mars?) and realizing just in time that a
> >>>> super-dense moon was orbiting rather low.
> >>>>
> >>>> I think of it as a Niven, but probably because I'm confusing it
> >>>> with There Is A Tide, where the moon was at normal height [...]
> >>>
> >>>http://www.isfdb.org/cgi-bin/title.cgi?45756
> >>>
> >>>Title: The Holes Around Mars
> >>>Author: Jerome Bixby
> >>>Year: 1954
> >>>Type: SHORTFICTION
> >>>Storylen: shortstory
> >>>Language: English
> >>>
> >>>Available for free at:
> >>>
> >>>https://www.gutenberg.org/ebooks/32360
> >> 
> >> "I think it's a calendar! ... Six hundred and eighty-seven squares in
> >> all.  That's how many days there are in the Martian year!"
> >> 
> >> WTF!  Why would a calendar devised by MARTIANS for Mars be based on
> >> EARTH days?
> >
> >How well was the rotation period of Mars established in 1954?
> 
> Nobody should have assumed that it was exactly identical to Earth's,
> even for purposes of a farce.

It's actually pretty close you know.

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#422689 — Re: YASID: Moon in a very low orbit.

Greg Goss <gossg@gossg.org> wrote in news:d5kn6uFijpuU1@mid.individual.net:

> Cryptoengineer <treifamily@gmail.com> wrote:
> 
>>Don Kuenz <garbage@crcomp.net> wrote in news:20150912a@crcomp.net:
>>'Orbital flight'? Or 'reaching orbital height'? There's a huge
>>difference in energy and guidance requirements. The latter is
>>much easier to do.
> 
> But what is "orbital height"?  I remember reading an SF short story
> about a guy wondering at the various holes and valleys on a planet he
> was exploring (Mars?) and realizing just in time that a super-dense
> moon was orbiting rather low.

'Orbital Height' is the lowest altitude at which something can be in
a stable, longlasting orbit. Around the Earth, and most planets, 
atmospheric drag is the limiting factor - the lowest Earth satellites
are about 100 miles up.

If there's no atmosphere, its high enough to clear the tallest 
mountain, though I suspect that close to the surface, irregularities
in gravity becomes a problem, and could perturb an otherwise good
orbit into one which intersects the surface.

pt

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#422711 — Re: YASID: Moon in a very low orbit.

"Cryptoengineer"  wrote
Greg Goss <gossg@gossg.org> wrote

>> But what is "orbital height"?  I remember reading an SF short story
>> about a guy wondering at the various holes and valleys on a planet he
>> was exploring (Mars?) and realizing just in time that a super-dense
>> moon was orbiting rather low.

> 'Orbital Height' is the lowest altitude at which something can be in
a stable, longlasting orbit. Around the Earth, and most planets,
atmospheric drag is the limiting factor - the lowest Earth satellites
are about 100 miles up.

> If there's no atmosphere, its high enough to clear the tallest
mountain, though I suspect that close to the surface, irregularities
in gravity becomes a problem, and could perturb an otherwise good
orbit into one which intersects the surface.

There is also the Roche limit for any satellite large enough for self 
gravitational forces to make a difference

https://en.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_examples 

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#422723 — Re: YASID: Moon in a very low orbit.

"Michael R N Dolbear" <me@privacy.net> wrote in
news:d5luasFskdvU1@mid.individual.net: 

> "Cryptoengineer"  wrote
> Greg Goss <gossg@gossg.org> wrote
> 
>>> But what is "orbital height"?  I remember reading an SF short story
>>> about a guy wondering at the various holes and valleys on a planet
>>> he was exploring (Mars?) and realizing just in time that a
>>> super-dense moon was orbiting rather low.
> 
>> 'Orbital Height' is the lowest altitude at which something can be in
> a stable, longlasting orbit. Around the Earth, and most planets,
> atmospheric drag is the limiting factor - the lowest Earth satellites
> are about 100 miles up.
> 
>> If there's no atmosphere, its high enough to clear the tallest
> mountain, though I suspect that close to the surface, irregularities
> in gravity becomes a problem, and could perturb an otherwise good
> orbit into one which intersects the surface.
> 
> There is also the Roche limit for any satellite large enough for self 
> gravitational forces to make a difference
> 
> https://en.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_exa
> mples 

That's true, but it applies only to objects with low tensile strength
for their size, and varies according to the size and strength of the
body. For the Moon around the Earth, its between 9k and 18k km, 
depending on the rigidity of the Moon. 

That is far higher than LEO satellites, which a built of much
sturdier stuff, and are a lot smaller.

pt
 

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#422782 — Re: YASID: Moon in a very low orbit.

In article <XnsA514E2806ED82melchizedek@216.166.97.131>, 
treifamily@gmail.com says...
> 
> "Michael R N Dolbear" <me@privacy.net> wrote in
> news:d5luasFskdvU1@mid.individual.net: 
> 
> > "Cryptoengineer"  wrote
> > Greg Goss <gossg@gossg.org> wrote
> > 
> >>> But what is "orbital height"?  I remember reading an SF short story
> >>> about a guy wondering at the various holes and valleys on a planet
> >>> he was exploring (Mars?) and realizing just in time that a
> >>> super-dense moon was orbiting rather low.
> > 
> >> 'Orbital Height' is the lowest altitude at which something can be in
> > a stable, longlasting orbit. Around the Earth, and most planets,
> > atmospheric drag is the limiting factor - the lowest Earth satellites
> > are about 100 miles up.
> > 
> >> If there's no atmosphere, its high enough to clear the tallest
> > mountain, though I suspect that close to the surface, irregularities
> > in gravity becomes a problem, and could perturb an otherwise good
> > orbit into one which intersects the surface.
> > 
> > There is also the Roche limit for any satellite large enough for self 
> > gravitational forces to make a difference
> > 
> > https://en.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_exa
> > mples 
> 
> That's true, but it applies only to objects with low tensile strength
> for their size, and varies according to the size and strength of the
> body. For the Moon around the Earth, its between 9k and 18k km, 
> depending on the rigidity of the Moon. 
> 
> That is far higher than LEO satellites, which a built of much
> sturdier stuff, and are a lot smaller.
> 
> pt
>  

Or to put it another way, if we can launch something for which the Roche 
limit is an issue, we have solved the launch problem.

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#422840 — Re: YASID: Moon in a very low orbit.

On 9/14/2015 3:05 AM, J. Clarke wrote:
> In article <XnsA514E2806ED82melchizedek@216.166.97.131>,
> treifamily@gmail.com says...
>>
>> "Michael R N Dolbear" <me@privacy.net> wrote in
>> news:d5luasFskdvU1@mid.individual.net:
>>
>>> "Cryptoengineer"  wrote
>>> Greg Goss <gossg@gossg.org> wrote
>>>
>>>>> But what is "orbital height"?  I remember reading an SF short story
>>>>> about a guy wondering at the various holes and valleys on a planet
>>>>> he was exploring (Mars?) and realizing just in time that a
>>>>> super-dense moon was orbiting rather low.
>>>
>>>> 'Orbital Height' is the lowest altitude at which something can be in
>>> a stable, longlasting orbit. Around the Earth, and most planets,
>>> atmospheric drag is the limiting factor - the lowest Earth satellites
>>> are about 100 miles up.
>>>
>>>> If there's no atmosphere, its high enough to clear the tallest
>>> mountain, though I suspect that close to the surface, irregularities
>>> in gravity becomes a problem, and could perturb an otherwise good
>>> orbit into one which intersects the surface.
>>>
>>> There is also the Roche limit for any satellite large enough for self
>>> gravitational forces to make a difference
>>>
>>> https://en.wikipedia.org/wiki/Roche_limit#Roche_limits_for_selected_exa
>>> mples
>>
>> That's true, but it applies only to objects with low tensile strength
>> for their size, and varies according to the size and strength of the
>> body. For the Moon around the Earth, its between 9k and 18k km,
>> depending on the rigidity of the Moon.
>>
>> That is far higher than LEO satellites, which a built of much
>> sturdier stuff, and are a lot smaller.
>>
>> pt
>>
>
> Or to put it another way, if we can launch something for which the Roche
> limit is an issue, we have solved the launch problem.
>
Hee hee hee.

-- 
Veni, vidi, snarki.

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#422745 — Re: YASID: Moon in a very low orbit.

On Sunday, 13 September 2015 16:31:27 UTC+1, Cryptoengineer  wrote:
> Greg Goss <gossg@gossg.org> wrote in news:d5kn6uFijpuU1@mid.individual.net:
> 
> > Cryptoengineer <treifamily@gmail.com> wrote:
> > 
> >>Don Kuenz <garbage@crcomp.net> wrote in news:20150912a@crcomp.net:
> >>'Orbital flight'? Or 'reaching orbital height'? There's a huge
> >>difference in energy and guidance requirements. The latter is
> >>much easier to do.
> > 
> > But what is "orbital height"?  I remember reading an SF short story
> > about a guy wondering at the various holes and valleys on a planet he
> > was exploring (Mars?) and realizing just in time that a super-dense
> > moon was orbiting rather low.
> 
> 'Orbital Height' is the lowest altitude at which something can be in
> a stable, longlasting orbit. Around the Earth, and most planets, 
> atmospheric drag is the limiting factor - the lowest Earth satellites
> are about 100 miles up.

IIRC, every supply mission to the International Space Station,
or many of them, also has a job of pushing the station back up,
since atmospheric drag brings it down.  I don't know what the
math is on how long until it crashes, if they don't do that,
several times a year (?)

So, does that count as "longlasting"?

> If there's no atmosphere, its high enough to clear the tallest 
> mountain, though I suspect that close to the surface, irregularities
> in gravity becomes a problem, and could perturb an otherwise good
> orbit into one which intersects the surface.

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#422803 — Re: YASID: Moon in a very low orbit.

Robert Carnegie <rja.carnegie@excite.com> wrote:
>On Sunday, 13 September 2015 16:31:27 UTC+1, Cryptoengineer  wrote:

>> 'Orbital Height' is the lowest altitude at which something can be in
>> a stable, longlasting orbit. Around the Earth, and most planets, 
>> atmospheric drag is the limiting factor - the lowest Earth satellites
>> are about 100 miles up.
>
>IIRC, every supply mission to the International Space Station,
>or many of them, also has a job of pushing the station back up,
>since atmospheric drag brings it down.  I don't know what the
>math is on how long until it crashes, if they don't do that,
>several times a year (?)
>
>So, does that count as "longlasting"?

If I recall, the original plan for the space shuttle was that the
second mission would be to push Skylab into a higher orbit.  But there
were bureaucratic delays and Skylab was gone before the shuttle
arrived.

First mission, of course, was to reach orbit and survive re-entry.
-- 
We are geeks.  Resistance is voltage over current.

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#422817 — Re: YASID: Moon in a very low orbit.

In <d5oah9Fgba8U1@mid.individual.net> Greg Goss <gossg@gossg.org> writes:

>If I recall, the original plan for the space shuttle was that the
>second mission would be to push Skylab into a higher orbit.  But there
>were bureaucratic delays and Skylab was gone before the shuttle
>arrived.

>First mission, of course, was to reach orbit and survive re-entry.

        'Original' is kind of a stretch.  But it was figured that an 
early Shuttle flight would have the mission of raising Skylab's orbit, 
with the possibility that it might be restocked and used for its own 
merits.  After the Skylab 4/3 flight in 1974 the space station was 
put in an orbit that, projections indicated, it should be able to keep 
for a decade or so.  And at the time, the first shuttle flights were 
forecast for around 1979, which should provide plenty of margin for 
unexpected developments.  Had upper-atmospheric models been better, 
that is, if they had been able to use the data Skylab collected, then 
just how thin the margin was would have been appreciated.  

        One sketchily developed plan for the use of Apollo hardware 
in case the Apollo-Soyuz Test Project collapsed was to send that Apollo 
to Skylab for a three-week-or-so mission.  This surely would have 
included a boost to the station's orbit.  But this Skylab backup plan 
wasn't developed far, in part because having too clear a plan in case 
the Soviets pulled out would increase the chance of the Soviets pulling 
out.  

-- 
                                                                Joseph Nebus
 Math: Reading the Comics, September 6, 2015 Edition    http://wp.me/p1RYhY-QT
Humor: Peeking In On The ThunderCats                    http://wp.me/p37lb5-XS
--------------------------------------------------------+---------------------

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